OpenGL 画出雷达动态扫描效果(一)

最终效果如下所示

Demo下载  http://files.cnblogs.com/xd-jinjian/Debug.zip

源代码下载 http://download.csdn.net/detail/xdjinjian/8266927

绘制扫面线部分代码如下，扫面部分可改进使用粒子系统，以增加真实感。

    glBegin(GL_TRIANGLE_FAN);
    glColor4f(0.0f, 0.0f, 0.0f,1.0f);
    glVertex2f(0.0f, 0.0f);    

    for(int i=;i<N;++i)
    {
        pos_x=cos((i/180.0)*Pi+theta)*R;
        pos_y=sin((i/180.0)*Pi+theta)*R;
        glColor4f(0.0f, (i+0.01)/N, 0.0f,0.8f);
        glVertex2f(pos_x, pos_y);
    }
    glEnd();
    

雷达界面的框架部分使用纹理贴图完成，加载位图资源代码如下

int power_of_two(int n)
{
    if( n <=  )
        return ;
    return (n & (n-)) == ;
} 

GLuint load_texture(const char* file_name)
{
    GLint width, height, total_bytes;
    GLubyte* pixels = ;
    GLint last_texture_ID;
    GLuint texture_ID = ; 

        FILE* pFile = fopen(file_name, "rb");
    if( pFile ==  )
        return ; 

    // 读取文件中图象的宽度和高度
    fseek(pFile, 0x0012, SEEK_SET);
    fread(&width, , , pFile);
    fread(&height, , , pFile);
    fseek(pFile, BMP_Header_Length, SEEK_SET); 

    // 计算每行像素所占字节数，并根据此数据计算总像素字节数
        {
        GLint line_bytes = width * ;
        while( line_bytes %  !=  )
            ++line_bytes;
        total_bytes = line_bytes * height;
    } 

    // 根据总像素字节数分配内存
    pixels = (GLubyte*)malloc(total_bytes);
    if( pixels ==  )
            {
        fclose(pFile);
        return ;
    } 

    // 读取像素数据
    if( fread(pixels, total_bytes, , pFile) <=  )
    {
                free(pixels);
        fclose(pFile);
        return ;
    }
    {
       GLint max;
       glGetIntegerv(GL_MAX_TEXTURE_SIZE, &max);
       if( !power_of_two(width)
        || !power_of_two(height)
        || width > max
        || height > max )
       {
                       const GLint new_width = ;
            const GLint new_height = ; // 规定缩放后新的大小为边长的正方形
            GLint new_line_bytes, new_total_bytes;
            GLubyte* new_pixels = ; 

            // 计算每行需要的字节数和总字节数
            new_line_bytes = new_width * ;
            while( new_line_bytes %  !=  )
                                ++new_line_bytes;
            new_total_bytes = new_line_bytes * new_height; 

            // 分配内存
            new_pixels = (GLubyte*)malloc(new_total_bytes);
            if( new_pixels ==  )
            {
                free(pixels);
                fclose(pFile);
                return ;
            } 

                        gluScaleImage(GL_RGB,
                width, height, GL_UNSIGNED_BYTE, pixels, new_width, new_height, GL_UNSIGNED_BYTE, new_pixels); 

            // 释放原来的像素数据，把pixels指向新的像素数据，并重新设置width和height
            free(pixels);
            pixels = new_pixels;
            width = new_width; 

                       height = new_height;
       }
   }
   glGenTextures(, &texture_ID);
    if( texture_ID ==  )
    {
        free(pixels);
        fclose(pFile);
        return ;
    }
    glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture_ID);
    glBindTexture(GL_TEXTURE_2D, texture_ID);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
    glTexImage2D(GL_TEXTURE_2D, , GL_RGB, width, height, ,
    GL_BGR_EXT, GL_UNSIGNED_BYTE, pixels);
    glBindTexture(GL_TEXTURE_2D, last_texture_ID);
    free(pixels);
    return texture_ID;
} 

使用位图资源

texGround = load_texture("xxxxx.bmp");

纹理贴图

    glEnable(GL_TEXTURE_2D);
    glBindTexture(GL_TEXTURE_2D, texGround);
    glBegin(GL_QUADS);
        glTexCoord2f(0.0f, 0.0f); glVertex3f(-0.5f, -0.5f,-0.0f);
        glTexCoord2f(0.0f, 1.0f); glVertex3f(-0.5f, 0.5f,-0.0f);
        glTexCoord2f(1.0f, 1.0f); glVertex3f(0.5f, 0.5f,-0.0f);
        glTexCoord2f(1.0f, 0.0f); glVertex3f(0.5f, -0.5f,-0.0f);
    glEnd();

注意画图形时打开纹理混合，并关闭深度测试

    glDisable(GL_DEPTH_TEST);
    glEnable(GL_BLEND);